Means for detecting and locating subaqueous sounds



A. F. SYKES AND J. T. MACGREGOR-MORRIS.

MEANS FOR DETECTING AND LOCATING SUBAQUEOUS SOUNDS.

APPLICATION FILED FEB. I2. 1919.

A. F. SYKES AND 1. T. MACGREGOR-IVIORRIS.

MEANS FOR DETECTING AND LOCATING SUBAQUEOUS SOUNDS.

APPLICATION FILED FEB. I2. 1919.

Patented Nov. 3o, 1920.

5 SHEETS-SHEET 2. j@ 6:

` A. F. SYKES AND I. T. MACGREGDR-MORRIS.

MEANS FOR DETECTING AND LOCATING SUBAQUEOUS SOUNDS.

APPLICATION FILED FEE. I2, I9I9.

1,360,339. Patented Nov. 3D, 192D.

5 SHEETS-SHEET 3.

A. F. SYKES AND J. T. MACGREGOR-IVIORRIS.

MEANS FOR DEIECTING AND LOCATING SUBAQUEOUS SOUNDS.

APPLICATION FILED IEB. I2. 1919.

l ,360, 330., Patented Nov. 30,1920.

5 SHEETS-SHEET 4l A. F. SYKES AND J. T. MACGREGOR-IVIORRIS.

MEANS FOR DETECTING AND LOCATING SUBAQUEOUS SOUNDS.

APPLICATION FILED FEB. I2, I9I9.

5 SHEETS-SHEET 5.

29.20; fig/y;

resi.

.ADRIAN FRANCIS SYKES, 0F NEW BARNET, AND JOHN 'IYLTltNlERl MAcGREGrOR-MORRIS,

i OF HAMPSTEAD, LONDON, ENGLAND.

A:MEANS FOR DETECTING AND LOCATING SUBAQUEOUS SOUNDS.'

Specification of Letters Patent.

Patenten Nov. ac, 192e.-

Application filed February 12, 1919. Serial No. 276,582.

To all whom t may conce-rn:

Be it known that we, ADRIAN FRANoIs SYKES, a subject of the King of Great Brit.` ain, residing at Lorne Vllla, New Barnet, Herts, England, and JOHN TURNER MAC- GRnGon-MoRRis, a subject of the King of Great Britain, residing at 3 Lyndhurst road, Hampstead, London, England have invented new and useful Improved' eans for Detecting and Locating Subaqueous Sounds, of which the following a specification.

This invention relates to the detection of sound in water by the vibration of a body immersed therein and to means for augmenting the motion of the said body. It further consists in apparatus whereby the oscillation induced by the sound is either in fact or in effect reduced according to the direction of the incident sound.

By an immersed body we mean in this specification a body so immersed that the water can act upon two opposite faces thereof, that is, if the body is so orientated that one face is normal and opposed to the direction of propagation of the sound waves, the waves have access not only to that face but to the opposite face.

Thus we immerse a body in the water and detect vibration by any known means, but we` prefer to use a microphone. We com,- bine a microphone and an immersed body in .such a fashion that the apparatus only responds to differences of pressure occurring externally, that is, between one side of the instrument and the other. Our apparatus operates by the force derived from the momentum of the particles of the water; it is insensitive to the vibration of pressure occurring at any one point in the normal transmission of a sound wave.

Preferably the microphone is mounted upon a. mass which is acoustically insulated from the immersed body relative to which such body moves. In some cases, however, the microphone itself can be acoustically insulated without the use of an independent mass. p

To explain our invention better We proceed to outline briefly the actioniof sound on a bod immersed in the medium transmitting t e sound. The propagation of a wave through a medium such as Water inmersed in the liquid is slightly Varied in`- volumehowing to the changes of pressure; with this eHect we are not concerned; in all the apparatus presently to be described We seek to insure that any changes in the volume of the body immersed shall be without effect on the detecting mechanism. To the extent that the body possesses size the pressure 1s not uniform over the whole; thus a difference'of pressure will occur tending to induce motion in the direction lin which the sound is traveling. Moreover, if the body, by virtue ofinertiaor other* impedance, tends to resist motion, a larger difference of pressure is created. It is of course understood that when rrefer to pressure we mean the instantaneous divergence from the mean pressure. 4Hence it will be seen that an immersed body tends to vibrate in the direction in which the sound 1s proceeding and not at all in a direction at right angles thereto. A body such as a disk of some suitable meta-l obstructs the sound much less in the edge-on position than When 1t receives the sound on the face.

If a microphone shielded by a case from external influence is operated by the diskv referred to above, the response of the microthe incident sound.

In developing our apparatus We have found it desirable to reduce the density of the immersed body. This may be done either by the use of solids Whose density is naturally low, such as Wood or paraffin Wax; but preferably We employ a metallic body which is hollow so as to obtain a low apparent density. The detecting agent is located within the cavity, thereby obviating the need for a separate case and flexible connection, which are undesirable if it is possible to dispense with them.

Great care is taken in the design of the immersed body to insure that the micro-- phone is operated from a point which does not change in position in response to variations in pressure provided that this pressure variation is not due to the impact of the water.

Any body can be used as a detector 'subject to certain precautions. Thus, if the immersed body is a spherical shell suiciently rigid to avoid uncertain vibrations in the body itself, direction can be found bythe immersed body by combining two plates and a ring. By using thin plates and mechanicall connecting their centers, the action of t e apparatus is localized and the results augmented. The reason for this is pact of the sound is of low apparent density and forms an easier path for the sound.

i To increase still further the inherentl sensitiveness of the instrument we make u se of the conception of an aperture 1n an acoustically opaque screen. It can be shown theoretically that the am litude of the vibration in the vicinity o the free passage is greater thanin the disturbed wave. Accordingly we immerse a body in 'a hole in a screen of dense material and thereby obtain an increased response.

The body may be a disk or a hollow body and is referably flexibly supported in the hole. enerally we close entirely the hole by two plates or diaphragms and connect mechanically their center points so that they are constantly constrained to vibrate in phase and constitute in effect a single body. A number of such units may be arranged in a single screen.

When sharp tuning ofthe vibrating system is required, the immersed body is in a metallic contact 'with the screen; but where response is objectionable rubber washers are meised body.

interposed between the screen and the im- When the water is flowing past the locator from whatever cause, it may so ha pen that the form of the instrument or t e delicate nature thereof may render screening unnecessary. In' such a case we inclose the instrument in an acoustically transparent shield filled with water, and provide means for rotating the instrument within the shield. In an elaborate form the shield is torpedo-shaped suitable for being towed,

and t el orientation of the instrument situated within is changed according to th strength of anelectric current.

that the portion -which responds to thev im- Our invention is illustrated by the accomanying drawings which show various orms of instrument constructed in accord- Figs. 5 and 6 are sections at right angles to one another of an instrument in which the mass and microphone are contained Within the detecting body.

Figs. 7 and 8 are a transverse section and a side viewV with one plate removed lof an instrument which may be re arded as a development of that shown in Y igsi and 6.

Figs. 9 and 10 show a different form ot apparatus. Figs. 11 and 12 show details an Figs. 13 to 16 are transverse sections of modified forms of instrument.

Figs. 17 and 18 show details.

Figs. 19 and 20 are a front view and section of a modified form of instrument.

In Figs. 1 and-2 thedetecting body isa disk l` attached to a lever 2 passing up through a flexible sleeve 3 which connects it to a case The lever is attached by means of a spring strip 5to a mass 6-which is acoustically insulated from the case 4 a group of rubber tubes 7. At the `upper end of the lever is mounted a microphone 8 from which fine conducting wires 9 lead to terminals' 10 carried by the mass. The case is supported by a tube 11 by means of which the instrument can be rotated in the water in which it is immersed and which also serve to contain the electric leadsp12 supplying currents tothemicrophone. Sound waves imiinging on the disk edge-on, as illustrate in Fig. 3, cause much less vibration and much less sound in the microphone than when the strike the face of the disk as in Fig. 4. n this case therefore the directive action is determined by the shape of the immersed body.

The whole is contained in a. shield 13 which is acousticall transparent and is filled with water.' his screen shields the disk from the direct impact of the water while permitting the sound to pass through.

In Figs. 5 and 6 the detecting body is formed of' a banjo shaped ring 14 with two ycover plates 15 connected to ther. The mass' 6 is as before acoustics y insulated by rubber` 7 Aand to it is attached the lever 2 which/is also connected to the body by means of a rubber bush 16 carriedb a fitting 17 at the bottom of thefbody. T e connection between the mass and the lever consists of two metallic leaves 18 secured to thefmass and to a cross" bar 181 fixed to the lever.

When the apparatus is immersed in water transmitting sound it 'oscillates chiefly as a whole in, the direction to which the sound l terior mechanism.

InYFigs.l 7 and 8 the ring 14 is cylindrical and the;y two side plates are lconnected to-v getherl at their centers by a strut or tie-bar 19,- (which `maybe formed of` a tube). From a point on this bar, preferably the center point, a wire or link 20 transmits vibrations to a lever 2 which is torsionally pivoted to the'mass 6, which as before is acoustically insulated from the ring- 14. This lever actuates the' microphone 8. Under favorable conditions the lever magniies the vibrations of the bar 19 and thus the response of the microphone. As the lever is connected by a torsion pivot' to the mass, which is acoustically insulated from the ring, the microphone can'only be influenced by vibration transnfiittedb throughl the connecting link 20. This link'ha's the property of transmitting only components of vibration in the direction offits'length; hence when the instrument vibrates in response to the sound the resolved part of the vibration in the direction of the connecting link alone affects the microphone. Thus the microphonegives a loud response when the outer surfaces of the plates 15 are at right angles'to the direction of propagation of the waves.

In Figs. 9 and 10 the detecting body is` formed of two hollow hemispheres 21 connected together by a diametrical plate 22 4and supported on a flexible stalk 23 rising up from a base 24, adapted to rest at the bottom of the sea. The mass 6 is mounted on the diametrical plate through the center of which passes a strut or tie-bar 19 to which the lever 2 is connected by a link as before.

The instrument osoillates as a whole in the direction in whichf the sound is being propagated. The sound produced inthe microphone due tothe impact of the sound waves is a maximum when such waves are traveling in the direction of the link 20 and is a minimum, that is, practically zero when the direction of propagation is at right angles thereto. In this case the back of the microphone is preferably carried by a counterbalanced arm 25 which isconnected by a pivot to the lever 2, which in its turn as before is pivoted to the mass 6 as shownv in Figs. 11 and 12.

Fig. 13 shows another form of instrument which may be looked upon as a development of that shown in Figs. 7 and 8. The

ring 14 is closed by two cover plates 151,

rubber rings 26 being inter osed between the plates and the r1ngs: 4he plates are recessed so as to be more flexible at their centers than at their peripheries. 27 arev rings covering the junctions between the parte so as to renderthe whole watertight.

ound striking the apparatus broadside on evades, asindicated by the arrows, the parts less free to move, and concentrates on the centers of the plates where the maximum sensitlveness occurs. The vibration induced largely exceeds in amplitude the motion of the water in the unobstructed wave. Thus the instrument, itself inherently discrimiv native owing to the disposition of the materia-l, is rendered still more so by the direc tive link 20. The minimum of sound can be discovered with great precision.

Fig. 14 shows an instrument in which.v

the principle of concentrating the sound waves,`as described with reference to Flg.

13, is extended. 28 lis a massive slab of dense material which is immersed in the water and has in vit. a hole in lwhich the detecting body is located. This, body consists of a ring 14 and two side'plates-l" connected together by a strut or tie-'bar 19. The body is specifically light and is flexibly. attached to the slab by spring strips. 29. The electric leads 12 pass down through a hole in the slab and are sealed into the ring 14 by insulating plugs 30.

Fig. 15 shows a very similar instrument.

In this case the slab is form'edin two halves and the side plates 15 are'actually part of the slab. v

Fig. 16 shows a slightly modified form of the instrument shown in Fig. 14.- n this case the immersed body consists of two angedl plates 152 connected together by a light hollow tube 191 with coned ends. The body is supported by two rubber rings 291 let into grooves formed in the slab around the hole. y

In the three forms of instrument shown in Figs. 14, 15 and 16 ythe microphone may be supported directly by the strut or tlc-bar 19 is shown in Fig. 17. Fig. 18 shows a method by which the v1- brations of the strut or tie-bar are mechanically ampliied before they reach the microphone. The strut 19 carries a diaphragm 31 on which is mounted the microphone actuating lever 2 which passes through 'and carries another diaphragm 32 which itself carries a comparatively heavy ring 33.v Vibrations of the strut 19 are imparted to the diaphragm 31 and therefore to the lever 2, which accordingly rocks about the point where it passes through the diaphragm 32,

this point being held steady by the inertia ofthe rin 33.

The act1on of the apparatus comprising the combination of a heavy mass and an immersed body-is as follows In the broadside'position the influence of the screen o1'V slab is such that the flow .of

sound concentrates on the immersed bod while ,in the edge-onfposition the slab lshiel s the immersed body rom the sound. Hence the direction in which the sound is bein propagated is readily discovered. As in al the examples previously descrlbed, the alternations of pressure at any given polnt 1nc1- dental to the transmission of the sound wave is without efect on the mechanism situated within the immersed body; the instrumentsA only respond to external differences of pressure.

Figs. 19 and 20 show a more developed form of the instrument illustrated in Flgs. 14 to 16. In this case the slab 28 is some- -what of a lenticular form. It is connected to the supporting tube 11 by a holder 34 containing a number of rubber washers 35 inclosin air spaces 36, and hasat lts upper end a g and 37. Bv'this means the sla 28 is acoustically insulated from the tube y11.

body having b'th sides thereof immersed, a, mass acoustically insulated therefrom, a

micro hone carried by the mass and means where y the microphone is caused to respond to vibrations of the body.

2. Apparatus for detecting and locating subaqueousl sounds, consisting of a .hollow body having two opposite sides connected to vibrate yin unison exposed to the water and means located within the body for detecting the vibrations thereof. 1

3. In means for detecting and locating subaqueous sounds, the combination of a hollowbody, an acoustically insulated mass within the body, a4 microphone carried by the mass and means for transmitting vibrations from the body to the microphone and for preventing components of'vibrations at right angles to a given direction from affect# ing the microphone.

4. In means for detecting and locating subaqueous sounds, the combinationr of a ring, two plates secured o ne on either side thereof, lan acoustically insulated mass withmass and means for detectin' vibrations of the plates andy for mechanica ly eliminating certain components thereof.

7,v In means for detecting and locating subaqueous sounds', the combination of two plates, `a tiebar connecting them together, a ring separating the plates and a microphone mounted on the tiebar. 1

8. In means for detecting and locating subaqueous sounds, the combination of aI slab of dense materialhaving in it a hole, a pair of plates closing the ho e, a tiebar Vcoupling the plates together and means for detectin the vibrations of the tiebar.

9. n means `for detecting and locatin subaqueous sounds, the combination of a sla of densel material havin in it a hole, a air of plates closin the ho e, a tiebar coup in the lates toget er and a microphone carrie by t e tiebar:

10. In means for detecting and locating subaqueous sounds, the combination of a slab o f dense material having in it a hole, a pair of plates, closing the hole,lelastic material separating the plates from the slab, a tiebar coupling the plates together and means for detecting the vibratlons of the tiebar.

11. In means for detecting and Alocating subaqueous sounds, the combination of `a slab. of dense material havin in it a hole, a pair of plates closing the ho e, a tiebar couplin the plates together, a mass acoustically insu ated from the slab, a microphone carried by the mass and means whereby the vibrations of the tiebar actuate rthe microphone.

12. Apparatus for detecting and locatingl sounds comprising means responsive to sound waves in the direction of their travel, detecting means operated thereby, the body of said detecting means being acoustically insulated from said firstmentioned means, and means capable of transmitting components of vibrations to said detecting meansin one direction only.v v

13. Apparatus for detectingand locating sounds comprising means res nsive to sound waves in the direction of t eir travel,

detecting means operated thereby, the body and means for conducting vibrations to said `*of said detecting means being acoustically detecting means which conducting means is insulated from said first-mentioned means capable of transmitting components of vand mechanical means capable of transmitbrations in one direction only.

5 ting components of vibrations to said detect- In testimony that We claim the foregoing 15 ing means in one direction only. as our invention We have signed our names 14. Apparatus for detecting and locating this twenty-fifth day of January, 1919. subaqueous sounds, consisting of a body having two opposite sides exposed to the Water, ADRIAN FRANCIS SYKES- 10 means for detecting the vibrations thereof, JOHN TURNER MacGREGOR-MORRIS- 

